Tube bender



Oct. 5, 1948.

J. E. CONZELMAN, JR

TUBE BENDER 2 Shee'ts-Sheet 1 Filed March 24, 1945 Win.

INVENTOR ZELMAN JR.

JOHN E. .Co1v

ATTORNEY.

.Patented Oct. 5, 1948 John E. Conzelman,

Jr., San Diego, Calif., as-

signor to Solar Aircraft Company, 'San Diego, Calif, a corporation of California Application March 24, 1945, Serial No. 584,507 2 Claims. (Cl. 15348) This invention relates to the bending 'of tubular members and is particularly useful in re-shaping straight, thin tubes into non-linear shapes.

An object of the invention tubesinto irregular shapes at low cost.

A more specific object is to bend tubes without introducing objectionable wrinkles into the walls of the tubes and without excessively thinning the walls.

Other more specific objects and features of the invention will appear from the detailed description of the invention to follow.

Briefly, a straight, cylindrical tube is bent in accordance with the present invention by forcing the tube into a die having the desired shape, by the application of high fluid pressure within the tubing, with or without the application of additional force direct to the rear end of the tube.

The fluid pressure may be applied to the interior of the tube through a piston positioned within the tube and the die, suitable sealing means being employed between the piston and the inside wall of the tube to prevent fluid leakage therebetween while permitting the tube to move longitudinally past the piston. In some cases the fluid pressure is applied directly to the interior of the tubing, the front end of the tubing being closed to prevent escape of the fluid. In other cases, a suitable flexible liner having a closed front end may be positioned within the tube, in which event the front end of the tube to be bent can be open and friction between the tube and the liner relied upon to advance the tube with the liner.

A full understanding of the invention may be had from the following description of certain specific embodiments of the invention as disclosed in the drawing, in which:

Fig. 1 is a side elevation with parts shown in section of apparatus for bending closed-end tubes;

Fig. 2 is a detail sectional view illustrating the sealing structure between the piston and the tube in Fig. 1;

Fig. 3 is a plan view partly in section of the apparatus. shown in Fig. 1, the apparatus being shown in position at the beginning of the bending operation;

Fig. 4 is a view similar to Fig. 3 but showing a modification of the apparatus;

Fig. 5 is a view similar to Figs. 3 and 4 but showing still another modification of the invention; and

Fig. 6 is an enlarged detail section of the leading end of the tube and liner in Fig. 5.

is to accurately bend piston being supported 2 Fig. 1, there is disclosed press ID having a base ll supl2 and having a hydraulic ram l3 adapted to raise and lower a platen l4. There is interposed between the bed l2 and the platen M a die l5 which is made in two sections l6 and H for disassembly to remove a tube after it has been bent. As clearly appears in Fig. 1, the two die sections I 6 and I1 have a, curved plane of joinder l8 which extends-along the axis of a, hole l9 which extends transversely through the die. The hole I!) is of uniform circular cross-section throughout its length and has substantially the same diameter as the external diameter of the tube that is to be bent. Normally the two die sections I 6 and I! are held firmly together between the bed l2 and the platen l4 of the press. The upper die section i6 is preferably fixed to the platen l4 by bolts Mia and nuts 16b so that the upper die block Hi can be raised and lowered with the press platen l4.

As shown in Fig. 1, a straight tube 20 having a closed forward end-2| is to be bent by forcing it into the hole I 9 in the die. To this end a piston 22 of slightly smaller diameter than the internal diameter of the tube 20 is positioned within the latter just inside the right end of the die, the by a hollow piston rod 23, is supported by a bracket 24 bolted to a, rail 25 which extends horizontally from the bed l2 of the press. The bracket 24 has apertures through which are extended rods 26, the left ends of which are secured to a pressure foot 21 which bears against the rear end of the tube to be bent (tube 20). The right ends of the rods 26 are secured to a head 28 on the left end of the piston rod 29 of a piston 30 which is positioned in a hydraulic ram cylinder 3|, the latter being mounted on the rail 25.

Referring first to schematically a porting a bed the rear end of which A brace may be bolted to the underside of the rail 25 and bear against a, nut 32 on a bolt 33 extending from the base I I, to reinforce the rail.

Referring to Fig. 2, a suitable form of seal between the piston 22 and the tube to be bent consists of annular rubber rings 35 mounted in annular grooves 36 in the peripheral wall of the piston. The sealing rings 35 are normally circular in cross-section and of diameter somewhat greater than the depth of the grooves 36. When fluid pressure is applied to the rings as indicated by the arrows in Fig. 2, the rings are compressed between the grooves in the piston and the wall of the tube 20 to effect a seal therebetween, irespective of minor irregularities in the inner surface of the tube.

It will also bee observed from inspection of Fig. 3 that the front face of the piston 22 is connected by a hollow passage 38 through the piston 22 and the piston rod 23 to an external line '39 which can be connected through suitable valves (not shown) either to a source of pressure fluid or to an exhaust line. Likewise, opposite ends of the ram cylinder 3| are connected by lines 4|] and 4| to a source of fluid pressure or to an exhaust line by a valve or valves (not shown) a The structure so far described with reference to Figs. 1, 2 and 3 is operated as follows:

Initially the platen i4 and the upper die section l5 which is secured thereto are raised by means of the press ram IS. The tube to be bent is then inserted over the piston 22 and fittedagainst the pressure foot 21, as shown in Fig. 1, after which the platen is lowered to firmly press the upper die section l5 against the lower die section l1.

Pressure fluid is then admitted through the pipe 39 and passage 38 into the interior of the tube between the piston 22 and the closedend of the tube, and at the same time the pipe 40 is connected to exhaust and pressure fluid is admitted through the pipe 4| to apply fluid pressure in the rear end of the cylinder 3| to urge the piston to the left. As a result of the fluid pressure exerted against the closed end 2| of the tube 20 and the mechanical force applied through the pressure foot 21 to the rear end of the tube from advanced over the the piston 30, the'tube 20 is piston 22. into the die i5 as shown in Fig. 3, after which the pressure is relieved in the line 39 and in the line 4| and pressure fluid is applied to the line 40 to retract the piston 30 and the pressure foot 21. The platen of the press is then raised and the bent tube is removed by lifting it out of the lower die section l1, together with the piston assembly, inciuding the piston 22, rod 23, and pressure foot 21. Thereafter the tube is pulled off the piston In some instances the hydraulic pressure applied through the piston 22 to the interior of the tube to be bent i suflicient to force the tube into the die and it is not necessary to provide the pressure foot 21 and the hydraulic ram 3|. In other instances, it is necessary or desirable to utilize both the hydraulic pressure within the tube and mechanical force on the rear edge of the tube to force the latter into the die.

As is apparent from inspection of Figs. 1 and 3, the hole in the die may be bent in two planes and the operation is not confined to the bending of tubes in a single plane.

It may be necessary or desirable in some instances to reinforce the end wal1 2| of the tube to enable it to withstand the hydraulic forces which may be in the neighborhood of four thousand pounds per square inch. A suitable lubricant should, of course, be applied to the interior surface of the hole IS in the die or to the exterior surface of the tube to be bent in order to maintain the sliding friction between the tube and the die at as low a value as possible.

Referring now to Fig. 4, the modification therein depicted differs from that of Figs. 1. and 3 in that the pressure foot for bearing against the rear end of the tube to be bent is eliminated, and the piston 22a is directly connected to the piston rod- 290. of the ram cylinder 3la and a plurality of balls 45 are inserted in the tube to be bent before the tube is positioned within the die.

In operating the modification shown in Fig.

4, the balls 45, which have a diameter equal to the internal diameter of the tube to be bent, are placed in the tube before the latter is placed on the piston 22a, and the ram stem 29a is retracted so that the tube lies in the straight portion of the hole in the die. Thereafter, hydraulic fluid under pressure is applied through the line 39a and the piston 22a to the interior of the tube to be bent, and at the same time fluid pressure is applied to the right end of the hydraulic ram 3m to move the piston 22a to the left. Movement of the tube into the bent portion of the hole in the in part by the fluid pressure developed against the closed end of the tube and, in part, by mechanical force applied by the piston 22a through the balls to the closed end of the tube.

It i to be noted that the function of the balls 45 is to transmit force directly from the piston 22dto the closed end 2la of the tube and not to prevent wrinkling or collapsing of the tube, the latter function being performed'by the pressure fluid within the tube. Functionally, the balls 45 of Fig. 4 are the equivalent of the pressure foot 21 in Fig. l.

The modification shown in Figs. 5 and 6 is for use in shaping open-ended tubes primarily, although it may also be used in closed end tubes, if desired. It difiers from the structure shown in the previously described figures in several respects. In the first place, the tube 201) to be bent is provided with a liner made of rubber or other flexible material through which the hydraulic pressure is applied to the tube. As best shown in Fig. 6, the main body of the liner 50 may be provided with a spiral reinforcing element 5| of metal or fabric and the closed end portion 52 of the liner may be reinforced with longitudinally extending reinforcing elements 53 to prevent the end of the liner from blowing out.

In order that the liner 50 carry the tube 20b along with it into the die, the outer' surface of the liner is treated or coated with some material having a high coefficient of friction. One material that has been found suitable for this purpose is obtainable in the market under the trade name of Loxite."

The arrangement shown in Fig. 5 also differs from the modifications shown in the other figures in that a piston within the tube to be bent has been eliminated and the rear end of the tube is extended through an opening 55 in the wall of a pressure chamber 55 which is adapted to be filled with fluid under pressure through a line 51. At its point of passage through the hole 55, the tube 20b may be sealed with the same type of seal shown in Fig. 2, except that the groove or grooves in which the annular rubber ring or rings are positioned are located in the wall of the hole 55 instead of in the piston 22, as shown in Fig. 2.

The pressure chamber 56 is preferably positioned with its front wall 58 as close as possible to the die l5 to reduce the danger of rupture-or expansion of the tube 20b between the pressure chamber and the die. It is to be understood that although spacing between the pressure chamber and the die is substantially as shown in Fig. 5, this spacing can, in practice, be reduced to a very low value.

At the beginning of a bending operation with the apparatus shown in Fig. 5, the tube 20b and the liner 50 are in the position shown in broken lines. When pressure is developed in the pressure chamber 56 by the admission of fluid through the line 51, the pressure is applied to the die is, therefore, effected only longitudinally.

closed end of the liner 50 and forces the latter and the tube 20b into the die as shown in full lines in Fig. 5. Thereafter. the pressure is removed from the pressure chamber, the die is opened up, and the tube 20b pulled out through the opening 55 in the pressure chamber. Thereafter, the liner 50 may be removed from the tube by pulling on one end or the other. Longitudinal tension applied to one end of the liner elongates it longitudinally and simultaneously reduces its diameter so that it releases itself from looking engagement with the tube 20b, despite the fact that the coating on the outer surface of the liner may have high friction characteristics.

In all of the various modifications of the invention described, the fluid pressure acts laterally against the side wall of the tube to force the latter out against the die and produce a finished product of the full diameter of the die and having a relatively smooth surface free from objectionable wrinkles.

The drawings show a passage in the die that is of circular cross section throughout, being bent However, it is to be understood that the invention is not limited to applying longitudinal bends to tubes, but all the modifications of the invention except that shown in Fig. 4 can be used to produce shapes'of noncircular cross sectional shape, either with or without longitudinal bends. Of course, in each instance that portion of the hole in the die ad Jacent to the entry oriflce must be of crosssectional shape to fit the original tube, lateral deformation from non-circular shape being introduced into the die passage farther along.

Although for the purpose of explaining the invention, several specific methods of practicing it have been described in detail, various departures from the exact procedure described will be obvious to those skilled in the art and the invention is to be limited only to the extent set forth in the appended claims.

I claim:

1. Apparatus for bending a tubular member having a closed end, said apparatus comprising: a die defining a tubular hole of the desired configuration into which the closed end of said member is insertable; piston means adapted to seal within said member in sliding relation therewith: means for supporting said piston in stationary relation within the entrance of said hole in said die; means for applying, fluid under pressure from an external source within said tubular member between the closed end thereof and said piston means, whereby said fluid under pressure develops a force against the closed end of said member urging the member longitudinally into the hole of said die while simultaneously urging the sidewall of the tubular member against the die; means for advancing said piston means into said die with said tubular member; and means insertable in said tube for transmitting longitudinal force mechanically from said piston means to the closed end of said member.

2. Apparatus for bending a tubular member having a closed end, said apparatus comprising: a die defining a tubular hole of the desired configuration into which the closed end of said memher is insertable; piston means adapted to seal within said member in sliding relation therewith; means for supporting said piston in stationary relation within the entrance of said hole in said die; means for applying fluid under pressure from an external source within said tubular member between the closed end thereof and said piston means, whereby said fluid under pressure develops a force against the closed end of said member urging the member longitudinally into the hole in said die while simultaneously urging the sidewall of the tubular member against the die; a solid member adapted to abut longitudinally directly against said tubular member; and means for applying force to said solid member for application thereby to said tubular member to aid, said fluid pressure in urging said tubular member into said hole in the die.

JOHN E. CONZELMAN, JR.

REFERENCES CITED The following references are of record in the file of this patent:

V UNITED STATES PATENTS Number Name Date 476,058 Moorfield May 31, 1892 1,329,969 Harrison Feb. 3, 1920 1,675,513 Parker July 3, 1928 1,947,611 Miotke Feb. 20, 1934 2,340,566 Ryder Feb. 1, 1944 OTHER REFERENCES Article Fluid Die Practice,"

Am. Machinist, Nov. 9, 1932, pages-1120-1123. 

